Heat fixing apparatus for fusible material



United States Patent [72] Inventor John F. Byrne [56] References Cited l 01110 UNITED STATES PATENTS [21] P 3,452,181 6/1969 Stryjewski 263/6(E) [22] Filed May 24,1968 I 45 P d N 10 1970 3,219,794 11/1965 Mmdell et al 219/388 1 "9" 3,331,592 7/1967 Cassano m1. 263/6(E) [73] Asslgnee Xerox Corporation Rochester, New York Pr mary Examiner.1ohn J. Camby a or oration of New York Attorneys-Norman E. Schrader, James J. Ralabate and Ronald Zibelli [54] IIEAT FIXING APPARATUS FOR FUSIBLE MATERIAL 3 Claims; Duwh ABSTRACT: A fixing system for fixing fusible material such [52] US. Cl. 263/6, as electroscopic particles upon support material. The system 219/388 includes two rollers in pressure contact between which the [51] Int. Cl. F27b 9/28, support material is transported. One of the rollers is provided F27g 3/12 with a heat barrier blanket and a release agent coating which [50] Field of Search 263/6(E): is adhesive to tackified particles in order to prevent offset" 219/388 thereof.

39 o n o o 0 Q o c Q Q h i .i' I f o t A 8 a L ,2 a j A g Paifit il Nov. 10, 1970 3,539,161

Sheet 2 of 3 INVENTOR. JOHN F. BYRNE w-xf TTORNEYS Patented Nov. 10, 1970 {539,161

heet or 3 mum JOH N E YRNE ATTORNEYS HEAT FIXING APPARATUS FOR FUSIBLE MATERIAL applying heat for fusing the powder. image'topaper is to bringthepowder image into direct contact with ahot surfaceysuch as a heated roller. But," as thepowder image :istackified-by heat, part of the image carried by the support materialwill offset" or stick to the surface of the heated roller so that as the next sheet is placed on the heat plate-,the taekified image.

partially removed from the first sheet will partlytransfer to the next sheet and, at the same time part of the -tackified image from said next sheet would adhere to the heated roller.

The offset" of toner onto the heated contacting surface.

has heretofore led to the rejection of contact fusers in favor of other heat fixing devices notparticularly suited for high speed copying/duplication, such as, coiled radiant element heaters with'refl'ectors. These radiant element'heaters with reflectors and other types such as the recirculating heated 'air type have the disadvantage of dissipating alarge quantity of heat into the machine enclosure in which they are used, heat transfer to the.

powder image is inefficient, and for the case of the coiled heater element they present a safety hazard becauseof the exposed element.

For some applications in offset prevention 'in aroll-fuser,

a tetrafluorethylene resin based material, such as, Teflon is utilized. This material has the physical characteristic of being. substantially adhesive to some tackifiedxerographic developing materials. However, its release or adhesive characteristic to some developing material, while .in a tackified' condition is not completely adequate for many of the more desirable developing particles at their fusing temperatures. To aid in offset" prevention, a fusing roller coated with Teflonmaterial is'usually coated with a thin film of silicon'e oil bymeans of an oil applicator wick. This arrangement requires an oil reservoirand wick supply and the periodic cleaning thereof.

Another disadvantage of this arrangementis the space needed; to house the reservoir and wick andattendent structure which' space is nearly the size of the fuser rollers and supports therefor.

It is, therefore, the principal object of this invention to improve the construction of a direct contactfusing device for toner images which will rapidly .fuse toner images without. causing the toner particles to smearwhilein a tackified state:

or to offset onto the device.

Another object of the invention-is to devisea fuser apparatus of relatively small size,'composed from relatively few parts, andeconomical to operate.

These and other objects of the invention are attained by means of a direct contact fusing'device in which thetoner image is fused by forwarding the sheetor-web ofpaper-bearingi toner images between two rollers, one-ofwhich-is heated and being provided with athin blanketof an insulatingmaterial such as silicone rubber and a coating of room temperature vul-- following detailed description of the inventionto be readin connection with the accompanying drawings, wherein:

FIG. 1 illustrates schematically a 'xerographic reproducing. apparatus adapted for high speed automatic operation, and incorporating'a roller heat fuser constructed in accordance with the invention;

FIG. 2 is a plane view, partly in section of the fuser apparatus shown in FIG. I;

FIG. 3 is an elevational view of the fuser assembly as seen from the rear of the machine;

FIG. 4 is an end view of the fuser assembly; as'seen'from the front of the machine;

FIG. '5.is a sectional view taken along the line-5 5 in FIG. 3;

and 1 FIG.- 6 is an enlargedfragmentary sectionalwiew of the peripheries of-the rollers utilized in the fuser apparatus.

For a general understanding of the illustrated copier/reproduction:machine; in which the invention may be incorporated, reference is had to FIG. 1 in which the various system components for the machine are schematically illustrated. As in all electrostatic systems such as a xerographic machineof the'type illustrated, a light image of a document to be reproduced is projected onto the sensitized'surface of axerographicw plate to form an electrostatic latent image thereon.-Thereafter, the latent image is developed with an op.- positely'charged developing material to form a xerographic powder image, corresponding to the latent image on the plate surface. The powder imageis then electrostatically transferred to a support surface to which it is fused by a fusing device whereby the powder image is caused permanently to adhere to the support surface.

In the illustrated machine, an original D to be copied is placed upon a transparent support platen P fixedly arranged in an illumination assembly generally indicated by-the reference numeral 10, arranged at the left end of the machine. The

- image rays are projected by means of an optical system for exof the.belt. The flash exposure of the belt surface to the light image discharges the photoconductive layer in the areas struck by light, whereby there remains on the belt a latent electrostatic image in image configuration corresponding to the light image projected .from the original on the supporting platen. As the belt surface continues its movement, the electrostatic image passes through a developing station B in which there islpositioned a developer assembly generally indicated by the reference numeral 14. The developer assembly 14 deposits developingmaterial' to the upper part of the belt assembly 11 whereat the material is directed to cascade down overthe upwardly moving inclined selenium belt 12 in order to provide development of the electrostatic image. As the developing material is cascaded over the xerographic plate, toner particles in the development material are deposited on the belt surface to form powder images.

The developer electrostatic image is transported by the belt to a transfer station C whereat a sheet of copy paper is moved at a speed in'synchronism with the moving belt in order to accomplish transfer of the developed image. There is provided at this station a sheet transport mechanism generally indicated at 16 adapted to transport sheets of paper from a paper handling mechanism generally indicated by the reference numeral 18 to the developed image on the belt at the station C.

After'thesheet is stripped from the belt 12, it is conveyed to I al, to separate and feed sheets ofpaper and to 'tranjsp ort'the same across the transfer station C and to, conveythesh'eet of paper through the fuser assembly in timed sequence to produce copies of the original. 2;

It is believed that the foregoing descriptionissufficient for the'purposes. of thisapplication to showthe generaloperation of an electrostatic'copier using an illuminatio n..s ystem conspaced apart end plates 25, 26 supported in parallel relation-I ship vertically bya base plate 27 secured to the main frame for the machine utilizing the fuser assembly. The frame is also relative to a common axis by means of a pivot pin 46 secured to the end plate and rotatably supporting the plate 44 and a second pivot pin 47 secured to the end plate 26 and pivotally supporting the plate 45. As the plates 44, 45 are pivoted in the provided with a rear brace 28 secured to the rear edges of 1 each of the plates 25, 26 and a brace 30 secured between the end plates at the forward section thereof.

Direct contact fusing of a powder image on a sheet of paper support material is achieved by forwarding a sheet bearing the powder image to be fused between a heated lower roller, generally designated 30, rotating into and under pressure during a fusing operation with an upper roller 31. The sheet of support material carrying the unfused toner images is directed between the nip of the rollers 30, 31 by means of guide rods 32 extending between the transport system 16 and the adjacent end of the fuser apparatus 20.

As shown in FIGSIZ, 5 and 6, the lower roller 30 comprises a supporting thin wall',"metallic cylinder 33 closed at both ends by caps 34 made of heat insulating material. Each of the caps 34 in turn is secured upon a shaft 35 which supports the roller 30 for rotation within the fuser assembly 20. The ends of the shaft 35 are rotatably mounted by bearings 36 upon the end plates 25, 26.

Surrounding the metallic cylinder 33 of the roller 30 is a heat insulating, silicone rubber blanket 37 having a radial thickness of sufficient dimension and, with some pliableness, to permit indentation thereof when the upper roller 31 is in pressure relationship therewith. Any other high temperature, and thermal insulation material may be utilized for the blanket 37, such as glass, cloth or other ceramic forms which can be made slightly pliable, as well as high temperature resisting foams or sealed elastomeric sleeves which can be made highly pliable. The blanket 37 in turn is coated with a thin coating 38 of a room temperature .vulcanizing compound, such as the same direction about the axis def ned by the pins 46, 47 the upper roller 31 is moved relative to the lower heated roller 30.

Pivotal movement of the upper roller support plates 44,45 is accomplished by means. of an air pressure actuated drive mechanism arrangedto impart pivotal movement to the plates in either direction to raise or'lower the upperroller 31 relative to the lower roller 30. The drive mechanism includes a cam member 50 in theform of aninclinedplane adapted to be moved horizontally for driving a cam f ollo wer 5 1 vertically.

The cam follower 5'1 is-in the form of a wheel adapted to ride upon the inclined plane of the cam member 50 and to be moved vertically in either direction from the position illus- Dow Corning Release Agent 236, produced by the Dow Corn- 1 ing Company. Since this material as such is highly reflective, it is preferred that it be mixed by approximately 5 percent by weight with the Dow Corning RTV 735 Sealant Adhesive which diminishes the reflective quality of the basic material heat barrier relative to the supporting structure for the roller 30. Another material that has exhibited suitable release characteristics for the newly produced low temperature melting toner'particles has been the silicone rubber material sold by Dow Chemical Corporation under their Trademark Silastic RV 501. Any other material may be utilized instead of a room temperature vulcanizing compound providing that its release properties remain effective ator above the fusing temperature of the toner particles bein g'fixed to a sheet of support material.

The upper roller 31 comprises a metallic cylinder 40 supported on a shaft 41 by means of caps 42 secured to the shaft and to the interior surface of each end of the roller. A coating 43 of insulating adhesive material such as, Teflon surrounds the cylinder 40 and should be of sufficient hardness to produce indentation of the materials 37', 38 on the roller 30 when in pressure contact. The shaft 41 is mounted at each end I in suitable bearings mounted on a pair of plates 44, 45'

trated in FIG. 3. The cam follower whee1l51 is rotatably mounted in a bracket 52 secured intermediate the ends of a cross brace 53. One end of the brace 53 extends beyond the end plate 25 and is connected to a link 54 which is connected by a pin 55 to the end of the plate 44. Similarly, the other end of the brace 53 is connected to a link 56 which is connected to the plate 45 by a pin 57. Upon movement of the inclined member 50 either to the left or right, as viewed in FIG. 3, the wheel 51 being held against horizontal movement will be moved vertically. Such movement of the cam follower produces corresponding movement of the cross brace 53 thereby moving both ends of the plates 44, 45 simultaneously and causing the roller 31 to move relativcto the lower fixed roller-31.

Actuation of the inclined plate 50 to the left or right as viewed in FIG; 3 is accomplished by means of an air cylinder and piston unit 58 connected by an air tubing 59 to a suitable supply 60 of air pressure. The supply 60 may in turn be connected to the machine logic for controlling movement of the roller 30, 31 into engagement for a fusing operation only at such times that a-sheet of support material is in position to be moved between the rollers.

The lower roller 30 is driven in the direction illustrated in FIG. 5 by the upper roller 31 during pressure contact therebetween. The shaft 41 for the upper roller 31 has a timing pulley 61 secured thereto and is drivingly connected by a timing belt 62 to the-drive system for the machine utilizing the fuser apparatus. When the roller 31 is in pressure contact with the roller 30, motion imparted to the shaft 41 and the roller 31 is imparted to the lower roller 30. As shown in FIG. 6, with the blanket 37 being pliable, the upper roller 31, having a periphery harder than that of the roller 30, when in pressure contact therewith forms a depression 63 of a sufficient arc length to aid in imparting the driving motion to the lower roller. More importantly, the arc length of the depression 63 also provides an extended time and surface that the lower roller 30 has with-the toner particles to be fused when a sheet of paper carrying the toner particles is being driven between the rollers.

As previously stated the lower roller 30 serves as the heated rounded by areflector 65 which also extends for the length of the lower roller, Thelamp 64 is mounted within the reflector 65 by suitable snapfclamps 66 secured each to an adjusting plate 67 adjustably mounted on each of the end plates 25, 26 respectively. The plates 67 may be adjusted relative to their respective end plates in order to position the heat lamp 64 selectively-toward or away from the lower roller 30 in accordance with the amount of heat to be imparted to an unfused toner image on a sheet of paper being transported between the rollers.

area of the roller thereby conserving energy for fusing purposes. in the event that additional heat is necessary for augmenting the heat generated by the lamp 64, the reflector housing is also provided with a ribbon heater 68 which is mounted to be in a heating position relative to the periphery of the lower roller. A suitable heat insulating cover 69 preferably circular in shape and concentric with the axis of theupper roller 31 is mounted on the upper edgesof the end plates 25, 26 immediately above the upper roller.

in operation, a sheet or web of support material such as paper is directed into the nip between the rollers 30, 31 in a manner wherein the toner image to be fused is on the lower surface of the horizontally moving transfer material. Radiant heat from the heat lamp 64 is applied to the outer surface of the roller 30.

Fusing is accomplished by the structure so far described by virtue of the. principles of low thermal mass. With heat being applied externally by the heat lamp 64 and/or the ribbon heater 67, the blanket 37 serves as a heat barrier to the heat applied externally thereby almost eliminating heat losses due to the roller 30, its supporting shaft 35 and the bearings which support the shaft for rotation in the fuser apparatus. The metallic parts for the lower roller 30 and its supporting structure then do not provide a heat sink for the heat generated upon the surface of the roller. With this arrangement, only a very small amount of heat from the lamp 64 will be needed to maintain the heat balance on the roller 30 in view of the loss of some heat through the rollers supporting structure. This results in the utilization of practically all of the heat produced by the lamp 64, except for the slight radiation and convective losses, for fusing purposes. In addition, the response time for the heating elements of the fuser (in condition to cause fusing properly) is relatively fast and, for high speed electrostatic copying or duplication, the heat that can be applied to the exroller. With less power requirements for the heating elements,

these are capable of longer life cycles and present little or no porting shaft for the rollers, the bearings supporting the same do not experience the usual heat that would be generated from heating elements positioned within the heater roll.

The coating 38 serves to prevent offset" of toner particles and, when in a tacky condition during a fusing operation, from adhering to the roller 30 and being brought into contact with the other portions of support material. As previously stated, the amount of heat that the radiant heating lamp 64 must supply is that which is given up to the toner particles and the support material to fuse the particles thereon plus the very small amount of heat that will be lost in being transferred from its point of application to the support material and to maintain the heat balance caused by the minimal losses through the supporting structure for the fuser rollers. This may be very precisely controlled to insure a minimum loss of heat. The use of low thermal mass concept for fusing configuration also assists in the prevention of toner offset in that this temperature may be more precisely controlled.

While the invention has been described with reference to the structure disclosed herein it is not confined to the details set forth and this application is intended to cover such modification or changes as may come with the purpose of the improvements or the scope of the following claims.

I claim: 1. A contact heat fusing apparatus of the type having a fusing member arranged for contacting thermoplastic particles in image configurationcarried on support material for fixing the image, the improvement comprising:

a thin heat insulating material associated with said fusing member and adapted as a barrier for the flow of heat; a coating of offset preventing material fixed upon said insulating material; and means for applying heat to said member during movement thereof, the heat being of sufficient quantity as to cause tackifying and fixing of the image upon the support material in contact with said member. 2. A contact heat fusing apparatus for fixing thermoplastic particles carried on a support material in image configuration, said apparatus including:

a support;

a first fusing member mounted for movement in an endless path on said support;

a second fusing member mounted for movement in an endless path on said support and positionable in contact with said first member, said members when in contact arranged to move support material therebetween with the image to-be-fixed in contact with one of the members;

said one member being formed therearound with a thin heat insulating material adapted as a barrier against the flow of heat and, a thin coating of offset preventing material fixed upon said material; and

means for applying heat to said one member during movement thereof, the heat being of sufficient quantity as to cause tackifying and fixing of the image upon the support material in contact with said one member. 7

3. A contact heat fusing apparatus for fixing thermoplastic particles carried on a support material in image configuration,

said apparatus including:

a fusing member mounted for movement in an endless path;

means for effecting the contacting of the image to be fixed with said fusing member;

said member comprising a support element and being structurally formed therearound with a thin coating of offset preventing, heat insulating material arranged to contact the images to be fused; and

means for applying heat to said fusing member during movement thereof, the heat being of sufficient quantity as to cause tackifying and fixing of the image upon the support material in contact with said coating on the fusing member.

5,2 3 UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3, 161 Dated November 10 1971 lnvent fl John F. Byrne It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

IN THE SPECIFICATION:

Line 6 of the ABSTRACT, change "adhesive" to -abhesive- Column 1, line 33, change "adhesive" to abhesive Signed and sealed this 10th day of August 1971 (SEAL) Atte st:

EDZ-IARD D'I.FLTGHEE-.,JR. WILLIAM E. SCHUYLER, JR. Attesting Officer Commissioner of Patents 

